Review request: 8009813 NMT should wait all collected data to be processed before generates report when PrintNMTStatistics option is specified

[Zhengyu Gu]

Hi David,

On 3/13/2013 6:52 PM, David Holmes wrote:
> On 14/03/2013 12:52 AM, Zhengyu Gu wrote:
>> This is a simple change that has NMT to wait for collected data to be
>> processed, before it prints out tracking data at JVM exit when
>> PrintNMTStatisitcs option is specified.
>
> I'm a little concerned as to whether it is always safe to perform the 
> actions that the wait performs, during this late phase of VM shutdown. 
> Is there any possibility that the thread we will wait for can not in 
> fact signal us? What is that thread and what might it be dooing?
>
The wait is on NMT worker thread. It waits NMT worker to make enough 
progress, so NMT can report memory usage that is fairly close to the 
state at JVM exit.  The NMT worker is shutdown after processing the 
report, if NMT is shutdown by other factors, the wait should abort.

BTW, PrintNMTStatistics is a JVM diagnostic. By default, it is off.

Thanks,

-Zhengyu


> Thanks,
> David
>
>> Without the wait, the data can be empty for short-lived application, or
>> might not match the data collected through other methods.
>>
>> JBS: https://jbs.oracle.com/bugs/browse/JDK-8009813
>> Webrev: http://cr.openjdk.java.net/~zgu/8009813/webrev.00/
>>
>> Test:
>>    - JPRT
>>    - vm.quick.testlist on Linux 32
>>
>>
>> Thanks,
>>
>> -Zhengyu